There is an increasing need to improve the level of security of public buildings, as well as specified areas within such buildings. One example includes the security of airport terminal buildings, which manage high volumes of passenger traffic on a daily basis. Typically, a specific region of an airport building may be designated as a ‘secure area’, wherein all personnel and their belongings are screened prior to entry into the secure area. Secure areas may include the departure lounge, and the gates used to assemble passengers prior to boarding the aircraft.
Baggage and other personal items can be screened using X-ray techniques and other techniques that are well known in the art. Such techniques permit analysis of the internal contents of the baggage for metallic items such as knives, guns, and explosive devices, as well as non-metallic illicit materials such as drugs and plastic explosives.
In contrast, passenger screening is not conducive to X-ray analysis, due to the potentially harmful effects of X-ray irradiation upon the human subject. Limited and carefully directed exposure to X-rays may be beneficial for medial diagnostic purposes. However, it is well known that exposure to X-rays should be avoided to minimize the risk of cellular and genetic defects. Therefore, it is unacceptable to expose airline passengers to X-rays on a routine basis for security purposes, particularly considering that whole-body irradiation would be required.
Commonly, the security measures employed for airline passenger screening include metal detectors. These metal detectors typically take the form of a freestanding doorway or ‘portal’ of sufficient size for a passenger to walk through unimpeded. The metal detectors simply sense the presence of metallic objects that may be concealed beneath the clothing or skin of the human. When the metal detector senses a quantity of metal that is above a pre-determined threshold, an alarm is trigger to alert the operator. The human passing through the metal detector may subsequently be subjected to a more thorough inspection, e.g. by passing a portable ‘wand-like’ metal detector in close proximity to the body and clothes of the human, to pinpoint the location of the metal more accurately.
Generally, passengers are not screened for objects other than metallic objects. This provides a window of opportunity for a would-be criminal to breach the security systems by attempting to smuggle illicit non-metallic objects into secure areas. Such illicit items may include for example drugs, plastic explosive materials, plastic or glass weapons, endangered animal parts etc. These items are generally of a size and shape that permits facile concealment beneath the clothing and/or the skin of a human. For this reason, there remains a strong need to develop security systems for use in airports and other secure locations, to detect such illicit objects and prevent their transfer into secure areas.